LED as a light source has been getting popular in the past years. There are many advantages for lighting fixtures configured with LED light sources. To name some of key advantages, energy saving, long life span, choices of color, flexible shape and space required to adopt LED light sources. Price was a concern for adopting this new technology before the volume would take off. Nowadays the price of LED light sources is well accepted and even more attractive lumens per dollar could be expected. One particular attribute may be related to current invention is its device size. Because of its tiny device size, an LED light source can be designed in a slim fixture. One example is a flat panel light being used for ceiling or wall mount. Because of slim thickness, probably less than 1 inch, it faces a challenge for designing a mounting system to easily install the flat panel light. A related art U.S. Pat. No. 9,453,616 discloses a technology using J-hooks at the edges of a mounting plate to engage a flat panel light at several sets of slots through slide-lock mechanism. The mounting plate is pre-secured to a target mounting surface. While the related art provides a way to install a thin flat panel light, however it does not offer a friendly way to do. In particular, it is not easy to have J-hooks reaching the slots without several attempts. The current invention discloses technologies to improve the drawback and also provides advantages.